Photoalignment Agent of Liquid Crystal, Photoalignment Film of Liquid Crystal Including the Same, and Liquid Crystal Display Including the Same

ABSTRACT

The present invention provides a liquid crystal photoalignment agent that includes a compound selected from the group consisting of a polyamic acid having a predetermined chemical formula, a polyimide polymer having a predetermined chemical formula, and a combination thereof, and a polyimide photopolymer. The liquid crystal photoalignment agent shows a long life-span, stably maintains a pretilt angle, and shows improved after-image characteristics, liquid crystal alignment properties, and chemical resistance.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a photoalignment agent of a liquidcrystal for a liquid crystal display (LCD) and a liquid crystalphotoalignment film made using the same. More particularly, the presentinvention relates to a photoalignment agent of a liquid crystal having along life-span, being capable of stably maintaining a pretilt angle,having improved after-image characteristics, and having excellent liquidcrystal alignment properties and chemical resistance.

(b) Description of the Related Art

A liquid crystal display (LCD) includes a liquid crystal alignmentlayer. The liquid crystal alignment film is mainly made of polymermaterials. The liquid crystal alignment film plays a role of a directorin aligning liquid crystal molecules. When the liquid crystal moleculesare moved by the influence of an electric field to display an image, theliquid crystal alignment film allows them to be oriented in apredetermined direction. Generally, it is necessary to uniformly alignthe liquid crystal molecules in order to provide uniform luminance and ahigh contrast ratio to the liquid crystal device.

The conventional method of aligning the liquid crystal includes coatinga polymer film such as a polyimide on a substrate made of a materialsuch as glass, and rubbing the surface of the substrate with a fibersuch as nylon or polyester in a certain direction. However, the rubbingmethod may cause serious problems while fabricating a liquid crystalpanel due to fine dust or electrostatic discharge (ESD) that may begenerated while rubbing the polymer film with the fiber.

In order to solve the problems of the rubbing method, thephoto-radiation method has recently been researched to induce anisotropyto the polymer film by irradiating light on the membrane so as to alignthe liquid crystal molecules.

As polymer film materials for the photoalignment method, polymers havingphoto-functional groups such as azobenzene, cumarin, chalcone, andcinnamate have been suggested. Such polymers are anisotropicallyphoto-isomerized or photo-cross-linked by being irradiated withpolarized light, so as to provide anisotropy to the surface so that itcan induce the liquid crystal molecules to align in a certain direction.

The material for the liquid crystal alignment film should have opticalstability and thermal stability, as well as no after-image in order toapply it a substantial liquid crystal display device (LCD). However, theconventional photoalignment materials have many troubles in thisrespect.

Further, the conventional material for the liquid crystal photoalignmentfilm is mainly polymeric that has a main chain of a polymer and a sidegroup of a photo-functional group that is capable of inducing thephoto-anisotropy, such as azobenzene or cinnamate. When the material fora polymeric liquid crystal photoalignment film is used, it may causeproblems not only in that a lot of photo energy is required to inducethe anisotropy, but also that the thermal stability, optical stability,and electro-optical characteristics are seriously affected by aplurality of unreacted remaining photo-functional groups.

SUMMARY OF THE INVENTION

An exemplary embodiment of the present invention provides aphotoalignment agent of a liquid crystal for a liquid crystal display(LCD) and a liquid crystal photoalignment film made using the same.

Another embodiment of the present invention provides a photoalignmentagent of a liquid crystal for a wide-viewing angle having stability fora change of operation conditions, high after-image-related reliability,stable strength for vertical alignment, and an excellent alignmentproperty for the liquid crystal, wherein the strength for the verticalalignment is not decreased when dropping the liquid crystal in the onedrop filling (ODF) method.

A further embodiment of the present invention provides a liquid crystalphotoalignment film prepared by the photoalignment agent of a liquidcrystal.

A further embodiment of the present invention provides a liquid crystaldisplay (LCD) including the liquid crystal photoalignment film.

The embodiments of the present invention are not limited to the abovetechnical purposes, and a person of ordinary skill in the art canunderstand other technical purposes.

According to one embodiment of the present invention, provided is aliquid crystal photoalignment agent that includes a compound selectedfrom the group consisting of polyamic acid represented by the followingChemical Formula 1, a polyimide polymer represented by the followingChemical Formula 2, a combination thereof, and a polyimide photopolymerrepresented by the following Chemical Formula 3.

In the above Formulae 1 to 3:

R₁, R₃, and R₅ are independently a quadrivalent organic group derivedfrom an acid dianhydride selected from the group consisting of analiphatic cyclic acid dianhydride and an aromatic acid dianhydride;

R₂ and R₄ are independently a divalent organic group derived from anaromatic diamine; and

R₆ is a divalent organic group derived from a photodiamine selected fromthe group consisting of a cumarin-based photodiamine, a chalcone-basedphotodiamine, and a cinnamate-based photodiamine.

According to another embodiment of the present invention, provided is aliquid crystal photoalignment layer that is produced by coating thephotoalignment agent of a liquid crystal on a substrate.

According to a further embodiment of the present invention, provided isa liquid crystal display (LCD) including the liquid crystalphotoalignment film.

Hereinafter, the embodiments of the present invention will be describedin detail.

The photoalignment agent of a liquid crystal according to one embodimentof the present invention has excellent optical and thermal stability andgood reliability with respect to after-images. Particularly, thephotoalignment agent of a liquid crystal can improve the display qualityin a liquid crystal display because it has a long life-span, it canstably maintain a pretilt angle, it improves after-imagecharacteristics, and it improves the liquid crystal alignment propertyand the chemical resistance. As a result, it is applicable to aphotoalignment agent of a liquid crystal for an LCD TV. Furthermore, theliquid crystal photoalignment film does not deteriorate the alignmentfilm properties due to the processes of the liquid crystal dropping orthe cleaning when fabricating an LCD panel.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross-sectional view of a liquid crystal display (LCD)according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the present invention will hereinafter bedescribed in detail. However, these embodiments are only exemplary, andthe present invention is not limited thereto.

The liquid crystal photoalignment agent according to one embodiment ofthe present invention includes a compound selected from the groupconsisting of a polyamic acid represented by the following ChemicalFormula 1, a polyimide polymer represented by the following ChemicalFormula 2, a combination thereof, and a polyimide photopolymerrepresented by the following Chemical Formula 3.

In the above Formulae 1 to 3:

R₁, R₃, and R₅ are independently a quadrivalent organic group derivedfrom an acid dianhydride selected from the group consisting of analiphatic cyclic acid dianhydride and an aromatic acid dianhydride;

R₂ and R₄ are independently a divalent organic group derived from anaromatic diamine; and

R₆ is a divalent organic group derived from a photodiamine selected fromthe group consisting of a cumarin-based photodiamine, a chalcone-basedphotodiamine, and a cinnamate-based photodiamine.

In the present specification, a substituted alkyl, a substitutedalkylene, a substituted cycloalkylene, a substitutedheterocycloalkylene, a substituted aryl, a substituted arylene, asubstituted heteroaryl, a substituted heteroarylene, a substitutedalkylaryl, a substituted pyrimidinyl, a substituted pyridinyl, asubstituted thiophenyl, a substituted furanyl, a substituted naphthyl,and a substituted phenyl are an alkyl, an alkylene, a cycloalkylene, aheterocycloalkylene, an aryl, an arylene, a heteroaryl, a heteroarylene,an alkylaryl, a pyrimidinyl, a pyridinyl, a thiophenyl, a furanyl, anaphthyl, and a phenyl that are independently substituted with ahalogen, a C1 to C30 alkyl, a C1 to C30 haloalkyl, a C6 to C30 aryl, aC2 to C30 heteroaryl, or a C1 to C30 alkoxy.

In the present specification, the heterocycloalkylene, heteroaryl, andheteroarylene respectively refer to a cycloalkylene, an aryl, and anarylene including 1 to 3 heteroatoms selected from the group consistingof nitrogen (N), oxygen (O), sulfur (S), and phosphorus (P), and theremainder being carbon.

The polyamic acid of the above Chemical Formula 1 is synthesized from adiamine selected from the group consisting of an aromatic diamine, afunctional diamine, and a combination thereof, and an acid dianhydrideselected from the group consisting of an aliphatic cyclic aciddianhydride, an aromatic acid dianhydride, and a combination thereof.

Copolymerization of the acid dianhydride and diamine to obtain polyamicacid can be performed according to conventional copolymerization.

The aliphatic cyclic acid dianhydride used during preparation ofpolyamic acid includes a compound selected from the group consisting of1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA),5-(2,5-dioxotetrahydrofuryl)-3-methylcyclohexene-1,2-dicarboxylic acidanhydride (DOCDA), bicyclooctene-2,3,5,6-tetracarboxylic aciddianhydride (BODA), 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride(CPDA), 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (CHDA),1,2,4-tricarboxyl-3-methylcarboxylcyclopentane dianhydride,1,2,3,4-tetracarboxyl cyclopentane dianhydride, and combinationsthereof, but is not limited thereto.

The quadrivalent organic group derived from the aliphatic cyclic aciddianhydride may be selected from the group consisting of compoundsrepresented by the following Chemical Formulae 4 to 8, and combinationsthereof.

In the above Formulae 4 to 8:

R₁₀ is a substituent selected from the group consisting of a substitutedor unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 toC30 aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, n₁₀is an integer ranging from 0 to 3; and

R₁₁ to R₁₇ are substituents independently selected from the groupconsisting of hydrogen, a substituted or unsubstituted C1 to C20 alkyl,a substituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl.

The aromatic acid dianhydride used during preparation of the polyamicacid includes a compound selected from the group consisting ofpyromellitic acid dianhydride (PMDA), biphthalic acid dianhydride(BPDA), oxydiphthalic acid dianhydride (ODPA), benzophenonetetracarboxylic acid dianhydride (BTDA), hexafluoroisopropylidenediphthalic acid dianhydride (6-FDA), and combination thereof, but is notlimited thereto.

The quadrivalent organic group derived from the aromatic aciddianhydride may include a structure selected from the group consistingof a compound represented by the following Formula 9, a compoundrepresented by the following Formula 10, and a combination thereof.

In the above Formulae 9 and 10:

R₂₁ and R₂₂ are independently a substituent selected from the groupconsisting of hydrogen, a substituted or unsubstituted C1 to C20 alkyl,a substituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl;

R₂₄ and R₂₅ are independently substituents selected from the groupconsisting of a substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl, and n₂₄ and n₂₅ are independentlyintegers ranging from 0 to 3; and

R₂₃ is selected from the group consisting of O, CO, a substituted orunsubstituted C1 to C6 alkylene such as C(CF₃)₂, a substituted orunsubstituted C3 to C30 cycloalkylene, and a substituted orunsubstituted C2 to C30 heteracycloalkylene, and n₂₃ is an integer of 0or 1.

The aromatic diamine used during preparation of polyamic acid includes acompound selected from the group consisting of paraphenylenediamine(p-PDA), 4,4-methylene dianiline (MDA), 4,4-oxydianiline (ODA),metabisaminophenoxydiphenylsulfone (m-BAPS),parabisaminophenoxydiphenylsulfone (p-BAPS),2,2-bis[(aminophenoxy)phenyl]propane (BAPP),2,2-bisaminophenoxyphenylhexafluoropropane (HF-BAPP),1,4-diamino-2-methoxybenzene, and combinations thereof, but is notlimited thereto.

The divalent organic group derived from the aromatic diamine may beselected from the group consisting of compounds represented by thefollowing Chemical Formulae 11 to 13, and combinations thereof.

In the above Formulae 11 to 13:

R₃₁, R₃₃, R₃₄, and R₃₇ to R₄₀ are independently substituents selectedfrom the group consisting of a substituted or unsubstituted C1 to C20alkyl, a substituted or unsubstituted C1 to C30 aryl, and a substitutedor unsubstituted C2 to C30 heteroaryl, and an alkyl, an aryl, and aheteroaryl including one selected from the group consisting of —O—,—COO—, —CONH—, —OCO— and combinations thereof;

R₃₀, R₃₂, R₃₅, and R₃₆ are independently substituents selected from thegroup consisting of O, SO₂, a C(R′)(R″) such as C(CF₃)₂ (where R′ and R″are independently selected from the group consisting of hydrogen and asubstituted or unsubstituted C1 to C6 alkyl);

n₃₁, n₃₃, n₃₄, and n₃₇ to n₄₀ are independently integers ranging from 0to 4; and

n₃₀, n₃₂, n₃₅, and n₃₆ are independently integers of 0 or 1.

The functional diamine used during preparation of polyamic acid causes aliquid crystal alignment film to control a pretilt angle of a liquidcrystal molecule and provides polyamic acid with excellent alignmentproperties. The functional diamine is selected from the group consistingof compounds of the following Chemical Formulae 14 to 16. Herein, thepolyamic acid includes a divalent organic group derived from thefunctional diamine.

In the above Formula 14:

R₄₁ is hydrogen, a substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, or a substituted orunsubstituted C2 to C30 heteroaryl,

R₄₂ is a substituent selected from the group consisting of a substitutedor unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 toC30 aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, andn₄₂ is an integer ranging from 0 to 3.

In the above Formula 15:

R₄₃, R₄₅, and R₄₆ are independently substituents selected from the groupconsisting of a substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to, C30 heteroaryl;

R₄₄ is a substituent selected from the group consisting of O, COO, CONH,OCO, and a substituted or unsubstituted C1 to C10 alkylene;

R₄₇ is a substituent selected from the group consisting of hydrogen, asubstituted or unsubstituted C1 to C20 alkyl, a substituted orunsubstituted C1 to C30 aryl, and a substituted or unsubstituted C2 toC30 heteroaryl, and an alkyl, an aryl, and a heteroaryl including oneselected from the group consisting of —O—, —COO—, —CONH—, —OCO—, andcombinations thereof;

n₄₃ is an integer of 0 or 3;

n₄₅ and n₄₆ are independently integers ranging from 0 to 4; and

n₄₄ is an integer of 0 or 1.

In the above Formula 16:

R₆₄ and R₆₆ are independently substituents selected from the groupconsisting of a substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl;

R₆₆ is a substituent selected from the group consisting of hydrogen, asubstituted or unsubstituted C1 to C20 alkyl, a substituted orunsubstituted C1 to C30 aryl, and a substituted or unsubstituted C2 toC30 heteroaryl;

R₆₁ and R₆₂ are independently selected from the group consisting of 0and COO;

R₆₃ is selected from the group consisting of O, COO, CONH, and OCO;

n₆₄ and n₆₆ are independently integers ranging from 0 to 4; and

n₆₁ to n₆₃ are independently integers of 0 or 1.

The polyimide polymer of the above Formula 2 may be prepared byimidization of the polyamic acid of the above Formula 1. The imidizationof the polyamic acid to obtain the polyimide polymer is well known inthis art and therefore detailed description thereof is not provided.

The polyimide photopolymer of the above Formula 3 can be synthesizedfrom at least one photodiamine, and an acid dianhydride selected fromthe group consisting of an aliphatic cyclic acid dianhydride, anaromatic acid dianhydride, and a combination thereof.

The copolymerization of the photodiamine and acid dianhydride to obtaina polyimide photopolymer is well known in this art, and therefore adetailed description thereof is not provided. The aliphatic cyclic aciddianhydride or aromatic acid dianhydride used during preparation of thepolyimide photopolymer is the same as one used during preparation of thepolyamic acid.

The photodiamine may be selected from the group consisting of acumarin-based photodiamine, a chalcone-based photodiamine, acinnamate-based photodiamine, and combinations thereof.

The cinnamate-based photodiamine may be selected from the groupconsisting of a compound of the following Formula 17, a compound of thefollowing Formula 18, and combinations thereof. The chalcone-basedphotodiamine is preferably a compound of the following Formula 19. Thecumarin-based photodiamine is preferably a compound of the followingFormula 20.

In the above Formula 17:

R₇₁ is selected from the group consisting of hydrogen, a substituted orunsubstituted C1 to C30 alkyl, a substituted or unsubstituted C6 to C30aryl, and a substituted or unsubstituted C2 to C30 heteroaryl; and

R₇₂ is selected from the group consisting of a substituted orunsubstituted C1 to C30 alkyl, a substituted or unsubstituted C6 to C30aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, and n₇₂is an integer ranging from 0 to 3.

In the above Formula 18:

R₇₇ is selected from the group consisting of an aromatic diamine, adiamine including a substituted or unsubstituted linear or branched C1to C24 alkylene, and combinations thereof;

the substituted alkylene of the R₇₇ is selected from the groupconsisting of a substituted alkylene where hydrogen is substituted witha substituent selected from the group consisting of a halogen and acyano, a substituted alkylene where at least one of CH₂ groups not beingadjacent to each other is substituted with a substituent selected fromthe group consisting of a substituted or unsubstituted C2 to C30arylene, a substituted or unsubstituted C2 to C30 heteroarylene, asubstituted or unsubstituted C3 to C30 cycloalkylene; a substituted orunsubstituted C2 to C30 heterocycloalkylene, —O—, —CO—, —CO—O—, —O—CO—,—Si(CH₃)₂—O—Si(CH₃)₂—, —NR′—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—,—O—CO—NR′—, —NR′—, —CO—NR′—, —CH═CH—, —C≡C—, and —O—CO—O— (where R′ isselected from the group consisting of hydrogen, and a substituted orunsubstituted C1 to C6 alkyl), and combinations thereof;

R₇₄ is a substituent selected from the group consisting of a substitutedor unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 toC30 aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, andn₇₄ is an integer ranging from 0 to 4;

R₇₆ and R₇₆ are independently selected from the group consisting ofhydrogen, a halogen, a cyano, and a substituted or unsubstituted C1 toC12 alkyl;

the substituted alkyls of the R₇₆ and R₇₆ are selected from the groupconsisting of a substituted alkyl where hydrogen is substituted with asubstituent selected from the group consisting of halogen and a cyano, asubstituted alkyl where at least one of CH₂ groups not being adjacent toeach other is substituted with a substituent selected from the groupconsisting of —O—, —CO—O—, —O—CO—, and —CH═CH—, and combinationsthereof,

R₇₃ is selected from the group consisting of a substituted orunsubstituted C1 to C30 alkyl, a substituted or unsubstituted C7 to C30alkylaryl, a substituted or unsubstituted C3 to C30 cycloalkyl, asubstituted or unsubstituted pyrimidinyl, a substituted or unsubstitutedpyridinyl, a substituted or unsubstituted thiophenyl, a substituted orunsubstituted furanyl, a substituted or unsubstituted naphthyl, and asubstituted or unsubstituted phenyl;

the substituted alkyl of the R₇₃ is selected from the group consistingof a substituted alkyl where hydrogen is substituted with a substituentselected from the group consisting of halogen and a cyano, a substitutedalkyl where at least one of CH₂ groups not being adjacent to each otheris substituted with a substituent selected from the group consisting of—O—, —OC—O—, —O—CO—, and —CH═CH—, and combinations thereof; and

the substituted alkylaryl of the R₇₃ is a substituted alkylaryl where atleast one of CH₂ groups not being adjacent to each other is substitutedwith a substituent selected from the group consisting of —O—, —OC—O—,—O—CO—, and —CH═CH—, and combinations thereof.

In the above Formula 19:

R₈₁ is selected from the group consisting of an aromatic diamine, adiamine including a substituted or unsubstituted linear or branched C1to C24 alkylene, and combinations thereof;

the substituted alkylene of the R₈₁ is selected from the groupconsisting of a substituted alkylene where hydrogen is substituted witha substituent selected from the group consisting of a halogen and acyano, a substituted alkylene where at least one of CH₂ groups not beingadjacent to each other is substituted with a substituent selected fromthe group consisting of a substituted or unsubstituted C2 to C30arylene, a substituted or unsubstituted C2 to C30 heteroarylene, asubstituted or unsubstituted C3 to C30 cycloalkylene, a substituted orunsubstituted C2 to C30 heterocycloalkylene, —O—, —CO—, —OC—O—, —O—CO—,—Si(CH₃)₂—O—Si(CH₃)₂—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—, —O—CO—NR′—,—NR′—, —CO—NR′—, —CH═CH—, —C≡C— and —O—CO—O— (where R′ is selected fromthe group consisting of hydrogen, and a substituted or unsubstituted C1to C6 alkyl), and combinations thereof;

R₈₂ and R₈₅ are substituents selected from the group consisting of asubstituted or unsubstituted C1 to C20 alkyl, a substituted orunsubstituted C1 to C30 aryl, and a substituted or unsubstituted C2 toC30 heteroaryl, and n₈₂ and n₈₅ are integers ranging from 0 to 4;

R₈₃ and R₈₄ are independently selected from the group consisting ofhydrogen, a halogen, a cyano, and a substituted or unsubstituted C1 toC12 alkyl; the substituted alkyls of the R₈₃ and R₈₄ are selected fromthe group consisting of a substituted alkyl where hydrogen issubstituted with a substituent selected from the group consisting ofhalogen and a cyano, a substituted alkyl where at least one of CH₂groups not being adjacent to each other is substituted with asubstituent selected from the group consisting of —O—, —OC—O—, —O—CO—,and —CH═CH—, and combinations thereof;

R₈₆ is selected from the group consisting of a substituted orunsubstituted C1 to C30 alkyl, a substituted or unsubstituted C7 to C30alkylaryl, a substituted or unsubstituted C3 to C30 cycloalkyl, asubstituted or unsubstituted pyrimidinyl, a substituted or unsubstitutedpyridinyl, a substituted or unsubstituted thiophenyl, a substituted orunsubstituted furanyl, a substituted or unsubstituted naphthyl, and asubstituted or unsubstituted phenyl;

the substituted alkyl of the R₈₆ is selected from the group consistingof a substituted alkyl where hydrogen is substituted with a substituentselected from the group consisting of a halogen and a cyano, asubstituted alkyl where at least one of CH₂ groups not being adjacent toeach other is substituted with a substituent selected from the groupconsisting of —O—, —OC—O—, —O—OC—, and —CH═CH—, and combinationsthereof; and

the substituted alkylaryl of the R₈₆ is a substituted alkylaryl where atleast one of CH₂ groups not being adjacent to each other is substitutedwith a substituent selected from the group consisting of —O—, —OC—O—,—O—CO—, and —CH═CH—, and combinations thereof.

In the above Formula 20:

R₉₁ is selected from the group consisting of an aromatic diamine, adiamine including a substituted or unsubstituted linear or branched C1to C24 alkylene, and combinations thereof;

the substituted alkylene of the R₉₁ is selected from the groupconsisting of a substituted alkylene where hydrogen is substituted witha substituent selected from the group consisting of a halogen and acyano, a substituted alkylene where at least one of CH₂ groups not beingadjacent to each other is substituted with a substituent selected fromthe group consisting of a substituted or unsubstituted C2 to C30arylene, a substituted or unsubstituted C2 to C30 heteroarylene, asubstituted or unsubstituted C3 to C30 cycloalkylene, a substituted orunsubstituted C2 to C30 heterocycloalkylene, —O—, —CO—, —OC—O—, —O—OC—,—Si(CH₃)₂—O—Si(CH₃)₂—, —NR′—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—,—O—CO—NR′—, —NR′—, —CO—NR′—, —CH═CH—, —C≡C—, and —O—CO—O— (where R′ isselected from the group consisting of hydrogen, and a substituted orunsubstituted C1 to C6 alkyl), and combinations thereof;

R₉₂ is a substituent selected from the group consisting of a substitutedor unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 toC30 aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, andn₉₂ is an integer ranging from 0 to 4;

R₉₃ and R₉₄ are independently selected from the group consisting ofhydrogen, a halogen, a cyano, and a substituted or unsubstituted C1 toC12 alkyl; and

the substituted alkyls of the R₉₃ and R₉₄ are selected from the groupconsisting of a substituted alkyl where hydrogen is substituted with asubstituent selected from the group consisting of a halogen and a cyano,a substituted alkyl where at least one of CH₂ groups not being adjacentto each other is substituted with a substituent selected from the groupconsisting of —O—, —C0-O—, —O—OC—, and —CH═CH—, and combinationsthereof.

The liquid crystal alignment agent includes 1 to 90 parts by weight ofthe polyamic acid or 1 to 50 parts by weight of the polyimide polymer,and 0.001 to 90 parts by weight of the polyimide photopolymer. Theliquid crystal alignment agent more preferably includes 1 to 90 parts byweight of the polyamic acid or 1 to 40 parts by weight of the polyimidepolymer, and 1 to 60 parts by weight of the polyimide photopolymer.

When the liquid crystal alignment agent includes all of the polyamicacid, the polyimide polymer, and the polyimide photopolymer, thepolyamic acid is included in an amount of 1 to 90 parts by weight, thepolyimide polymer is included in an amount of 1 to 50 parts by weight,and the polyimide photopolymer is included in an amount of 0.001 to 90parts by weight. Preferably, the polyamic acid is included in an amountof 1 to 90 parts by weight, the polyimide polymer is included in anamount of 1 to 40 parts by weight, and the polyimide photopolymer isincluded in an amount of 1 to 60 parts by weight.

When the liquid crystal alignment agent of the polyamic acid, thepolyimide polymer, and the polyimide is added within the range, theafter-image characteristics are particularly improved.

According to another embodiment of the present invention, provided is aliquid crystal photoalignment film that is provided by using thephotoalignment agent of a liquid crystal.

The liquid crystal photoalignment film may be obtained by adding thephotoalignment agent of a liquid crystal in a solvent to provide acomposition, and coating the same on a substrate to provide a liquidcrystal photoalignment film.

The solvent may include N-methyl-2-pyrrolidone, N,N-dimethyl acetamide,N,N-dimethyl formamide, dimethyl sulfoxide, γ-butyro lactone, and aphenol-based solvent such as a meta cresol, a phenol, a halogenatedphenol, and the like.

In addition, the solvent may further include a poor solvent such asalcohol series, ketone series, ester series, ether series, hydrocarbonseries, or halogenated hydrocarbon series solvents, as long as thesoluble polyimide polymer is not deposited. The poor solvent lowerssurface energy of a liquid crystal alignment agent and improves itsspread and flatness when the liquid crystal alignment agent is coated.

The poor solvent may be included in an amount of 1 to 90 volume % basedon the total amount of the solvent. In another embodiment, it may beincluded in an amount of 1 to 70 volume %.

Specific examples of the poor solvent include one selected from thegroup consisting of methanol, ethanol, isopropanol, cyclohexanol,ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol,acetone, methylethylketone, cyclohexanone, methyl acetate, ethylacetate, butyl acetate, diethyl hydroxide, malonic acid ester, diethylether, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol phenyl ether, ethylene glycol phenyl methylether, ethylene glycol phenyl ethyl ether, ethylene glycoldimethylethyl, diethylene glycol dimethylethyl, diethylene glycol ether,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,diethylene glycol monomethyl ether acetate, diethylene glycol monoethylether acetate, ethylene glycol methyl ether acetate, ethylene glycolethyl ether acetate, 4-hydroxy-4-methyl-2-pentanone, 2-hydroxy ethylpropionate, 2-hydroxy-2-methyl ethyl propionate, ethoxy ethyl acetate,hydroxy ethyl acetate, 2-hydroxy-3-methyl butanoic acid methyl,3-methoxy methyl propionate, 3-methoxy ethyl propionate, 3-ethoxy ethylpropionate, 3-ethoxy methyl propionate, methyl methoxy butanol, ethylmethoxy butanol, methyl ethoxy butanol, ethyl ethoxy butanol,tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane, trichloro ethane, chlorobenzene, o-dichlorobenzene, hexane,heptane, octane, benzene, toluene, xylene, and combinations thereof.

The amount of solvent is not limited in the composition for forming aliquid crystal photoalignment film, but according to one embodiment ofthe present invention, the solid amount of the photoalignment agent of aliquid crystal ranges from 1 to 30 wt %; in another embodiment, itranges from 3 to 15 wt %; and in a further embodiment, it ranges from 5to 10 wt %. When the solid amount is less than 1 wt %, it may causeproblems in that the film is affected by the printing process so thatthe film uniformity is deteriorated; on the other hand, when it is morethan 30 wt %, the film uniformity is deteriorated and the transmittanceis deteriorated due to the high viscosity during the printing process.

The composition for forming a liquid crystal photoalignment film mayinclude more than one epoxy compound having 2 to 4 epoxy functionalgroups to improve reliability and electro-optical characteristics. Theepoxy compound may be included in an amount of 0.01 to 50 parts byweight based on 100 parts by weight of the liquid crystal photoalignmentagent. In another embodiment, it may be included in an amount of 1 to 30parts by weight. When it is included in an amount of 50 parts by weightor more, it may deteriorate printability or flatness. When it isincluded in an amount of 0.01 parts by weight, it may have littleeffects of an epoxy compound. Specific examples of the epoxy compoundinclude N,N,N′,N′-tetraglycidyl-4,4′-diaminophenylmethane (TGDDM),N,N,N′,N′-tetraglycidyl-4,4′-diaminophenylethane,N,N,N′,N′-tetraglycidyl-4,4′-diaminophenylpropane,N,N,N′,N′-tetraglycidyl-4,4′-diaminophenylbutane,N,N,N′,N′-tetraglycidyl-4,4′-diaminobenzene, and so on, but it is notlimited thereto.

The composition for forming a liquid crystal photoalignment film canfurther include a silane coupling agent or a surfactant to improveadherence to a substrate, and flatness and coating characteristics.

The composition for forming a liquid crystal photoalignment film iscoated on a substrate to form a liquid crystal photoalignment film. Thecomposition for forming a liquid crystal photoalignment film can becoated in a method such as spin coating, flexo printing, Inkjetprinting, and the like. The flexo printing can accomplish excellentuniformity of a film and may easily form a larger liquid crystalphotoalignment film.

The substrate has no particular limit, but may include a glass substrateor a plastic substrate such as an acryl substrate or a polycarbonatesubstrate, as long as it is transparent. In addition, it may include asubstrate including an ITO electrode and the like for liquid crystaloperation in terms of simplifying a manufacturing process.

In order to improve uniformity of a film, the composition for forming aliquid crystal photoalignment film may be uniformly coated on asubstrate and predried at room temperature to 200° C., 30 to 150° C., or40 to 120° C., for 1 to 100 minutes. The predrying can controlvolatility of each component of the liquid crystal alignment agent,securing a uniform film without a thickness deviation.

Then, it is fired at a temperature of 80 to 300° C. or 120 to 280° C.for 5 to 300 minutes to completely evaporate a solvent, fabricating aliquid crystal alignment film.

The liquid crystal alignment film can be used for a liquid crystaldisplay with uniaxial alignment treatment by polarized ultraviolet (UV)rays or rubbing, or without the uniaxial alignment treatment for someuses such as a vertical alignment film and the like.

The liquid crystal photoalignment film according to one embodiment ofthe present invention can be subjected to uniaxial alignment treatmentby exposing to light with energy of 10 mJ to 5000 mJ for 0.1 to 180minutes. As mentioned above, the uniaxial alignment treatment can beperformed with a reduced exposure intensity so as to completely removedouble bonds included in the polyimide photopolymer.

According to a further embodiment of the present invention, provided isa display device including the liquid crystal photoalignment film. Inanother embodiment, the display device is a liquid crystal display(LCD).

FIG. 1 is a cross-sectional view showing a liquid crystal display (LCD)according to one embodiment of the present invention.

As shown in FIG. 1, the liquid crystal display (LCD) 1 according to oneembodiment of the present invention includes a lower panel 100, an upperpanel 200, and a liquid crystal layer 3.

In the lower panel 100, a gate conductor including a plurality of gatelines (not shown) and a plurality of storage electrodes 133 is formed ona front surface of a first substrate 110. On the gate conductor, a gateinsulating layer 140, a plurality of semiconductors 154, a plurality ofpairs of ohmic contacts 163 and 165, a plurality of source electrodes173, and a plurality of drain electrodes 175 are sequentially formed.

One thin film transistor (TFT) consists of one gate electrode 124, onesource electrode 173, and one drain electrode 175 together with asemiconductor 154.

A passivation layer 180 is formed on the exposed portion of thesemiconductor 154, the source electrode 173, the drain electrode 175,and the gate insulating layer 140. On the passivation layer 180, aplurality of pixel electrodes 191 are formed.

Hereinafter, the upper panel 200 is described.

In the upper panel 200, a light blocking member 220 is formed on asecond substrate 210. A plurality of color filters 230 is formed on thesecond substrate 210 and the light blocking member 220, and an overcoat250 is formed on the color filter 230. The overcoat 250 is to preventthe color filter 230 from being exposed to the liquid crystal layer 3,and the overcoat 250 can be omitted.

A first liquid crystal photoalignment film 12 is formed on the surfaceof the pixel electrode 191 of the lower panel 100, and a second liquidcrystal photoalignment film 22 is formed on the surface of a commonelectrode 270 of the upper panel 200. The first liquid crystalphotoalignment film 12 and the second liquid crystal photoalignment film22 are fabricated by using the photoalignment agent of a liquid crystalaccording to one embodiment of the present invention.

Even though the liquid crystal photoalignment films 12 and 22 are shownto be respectively formed on the lower panel 100 and the upper panel 200in FIG. 1, the liquid crystal photoalignment film 12 or 22 may be formedin either the upper panel 200 or the lower panel 100.

The following examples illustrate the present invention in more detail.These examples, however, should not in any sense be interpreted aslimiting the scope of the present invention.

Indeed, descriptions that are not included in this specification areomitted because they can be easily understood by one having ordinaryskill in the art without any difficulties.

Preparation Example 1 Preparation of Polyamic Acid (PAA-1)

0.7 moles of phenylenediamine and 0.3 moles of functional diamine3,5-diaminophenyldecyl succinimide of the following Chemical Formula 21were introduced into a four-necked flask mounted with an agitator, atemperature controller, a nitrogen gas injector, and a cooler whileflowing nitrogen therethrough, and N-methyl-2-pyrrolidone (NMP) wasadded thereto to provide a mixed solution.

1.0 mole of solid 1,2,3,4-cyclobutanetetracarboxylic acid dianhydridewas added to the mixed solution and vigorously agitated. The solidamount was 20 wt %. The reaction was performed while maintaining thetemperature between 30° C. and 50° C. for 10 hours to provide a polyamicacid resin. To the provided polyamic acid resin, a mixed organic solventof N-methyl-2-pyrrolidone and γ-butyrolactone was added and agitated atroom temperature for 24 hours to provide a polyamic acid solution(PAA-1).

Preparation Example 2 Preparation of Polyamic Acid (PAA-2)

A polyamic acid solution (PAA-2) was prepared in accordance with thesame procedure as in Preparation Example 1, except that the functionaldiamine represented by the following Chemical Formula 22 was usedinstead of the functional diamine represented by Chemical Formula 21.

Preparation Example 3 Preparation of Polyamic Acid (PAA-3)

A polyamic acid solution (PAA-3) was prepared in accordance with thesame procedure as in Preparation Example 1, except that the functionaldiamine represented by the following Chemical Formula 23 was usedinstead of the functional diamine represented by Chemical Formula 21.

Preparation Example 4 Preparation of Polyimide a Polymer (SPI-1)

0.8 moles of phenylenediamine and 0.2 moles of diamine3,5-diaminophenyldecyl succinimide represented by Chemical Formula 21were introduced into a four-neck flask mounted with an agitator, atemperature controller, a nitrogen gas injector, and a cooler whileflowing nitrogen therethrough, and N-methyl-2-pyrrolidone was addedthereto to provide a mixed solution.

To the mixed solution, 1.0 mole of solid1,2,3,4-cyclobutanetetracarboxylic acid dianhydride was introduced andvigorously agitated. The solid amount was 20 wt %. The reaction wasperformed while maintaining the temperature within 30° C. to 50° C. for10 hours to provide a polyamic acid solution.

After 3.0 moles of acetic acid anhydride and 5.0 moles of pyridine wereadded to the obtained polyamic acid solution and the temperature wasincreased to 80° C., it was reacted for 6 hours, and the catalyst andthe solvent were removed through vacuum distillation to provide asoluble polyimide resin having a solid amount of 20%.

To the obtained soluble polyimide resin, a mixed organic solvent ofN-methyl-2-pyrrolidone and γ-butyrolactone was added and agitated atroom temperature for 24 hours to provide a soluble polyimide resin(SPI-1).

Preparation Example 5 Preparation of Polyimide a Polymer (SPI-2)

A soluble polyimide resin (SPI-2) was prepared in accordance with thesame procedure as in Preparation Example 4, except that the functionaldiamine represented by the following Chemical Formula 22 was usedinstead of the functional diamine represented by Chemical Formula 21.

Preparation Example 6 Preparation of Polyimide a Polymer (SPI-3)

A soluble polyimide resin (SPI-3) was prepared in accordance with thesame procedure as in Preparation Example 4, except that the functionaldiamine represented by the following Chemical Formula 23 was usedinstead of the functional diamine represented by Chemical Formula 21.

Preparation Example 7 Preparation of Polyimide Photopolymer (PSPI-1)

0.5 moles of phenylenediamine and 0.5 moles of diamino benzoic acid4-(2-ethoxycarbonyl-vinyl)-phenyl ester represented by the followingChemical Formula 24 were introduced into a four-neck flask mounted withan agitator, a temperature controller, a nitrogen gas injector, and acooler while flowing nitrogen therethrough under a dark room condition,and N-methyl-2-pyrrolidone was added thereto to provide a mixedsolution.

In the above Formula 24, n=2.

To the mixed solution, 1.0 mole of solid1,2,3,4-cyclobutanetetracarboxylic acid dianhydride was added andvigorously agitated. The solid amount was 20 wt %. The reaction wasperformed while maintaining the temperature between 30° C. and 80° C.for 24 hours to provide a polyamic acid solution.

After 3.0 moles of acetic acid anhydride and 5.0 moles of pyridine wereadded to the obtained polyamic acid solution and the temperature wasincreased to 80° C., the reaction was performed for 6 hours, and thecatalyst and the solvent were removed with vacuum distillation toprovide a soluble polyimide photopolymer having a solid amount of 20%.

To the obtained soluble polyimide photopolymer, a mixed organic solventof N-methyl-2-pyrrolidone and γ-butyrolactone was added and agitated atroom temperature for 24 hours to provide a soluble photoalignmentpolyimide resin (PSPI-1).

Preparation Example 8 Preparation of Polyimide Photopolymer (PSPI-2)

A photoalignment polyimide resin (PSPI-2) was prepared in accordancewith the same procedure as in Preparation Example 7, except that 1.0mole of compound represented by Chemical Formula 24 was used.

Preparation Example 9 Preparation of Polyimide Photopolymer (PSPI-3)

A photoalignment polyimide resin (PSPI-3) was prepared in accordancewith the same procedure as in Preparation Example 7, except that 1.0mole of the compound represented by Chemical Formula 25 was used insteadof the compound represented by Chemical Formula 24.

Preparation Example 10 Preparation of Polyimide Photopolymer (PSPI-4)

A photoalignment polyimide resin (PSPI-4) was prepared in accordancewith the same procedure as in Preparation Example 7, except that 1.0mole of the compound represented by Chemical Formula 26 was used insteadof the compound represented by Chemical Formula 24.

Preparation Example 11 Preparation of Polyimide Photopolymer (PSPI-5)

A photoalignment polyimide resin (PSPI-5) was prepared in accordancewith the same procedure as in Preparation Example 7, except that 1.0mole of the compound represented by Chemical Formula 27 was used insteadof the compound represented by Chemical Formula 24.

Preparation of Liquid Crystal Photo-alignment Film Example 1

10 g of a PSPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 7 was introduced into 70 g of a PAA-1 solutionhaving a solid amount of 8 wt % obtained from Preparation Example 1,agitated while flowing nitrogen for 24 hours, then filtered though afilter having a sieve size of 0.1 μm to provide a photoalignment agentof a liquid crystal (hereinafter referred to as PAA/PSPI-1) having asolid amount of 8 wt %.

Example 2

10 g of a PSPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 7 was introduced into 20 g of an SPI-1 solutionhaving a solid amount of 8 wt % obtained from Preparation Example 4,agitated while flowing nitrogen for 24 hours, then filtered though afilter having a sieve size of 0.1 μm to provide a photoalignment agentof a liquid crystal (hereinafter referred to as SPI/PSPI-1) having asolid amount of 8 wt.

Example 3

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 10 g of a PSPI-1 solution having a solidamount of 8 wt % obtained from Preparation Example 7 were introducedinto 70 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-1) having a solid amount of 8 wt %.

Example 4

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 30 g of a PSPI-1 solution having a solidamount of 8 wt % obtained from Preparation Example 7 were introducedinto 50 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-2) having a solid amount of 8 wt %.

Example 5

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 50 g of a PSPI-1 solution having a solidamount of 8 wt % obtained from Preparation Example 7 were introducedinto 30 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-3) having a solid amount of 8 wt %.

Example 6

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 70 g of a PSPI-1 solution having a solidamount of 8 wt % obtained from Preparation Example 7 were introducedinto 10 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-4) having a solid amount of 8 wt %.

Example 7

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 10 g of a PSPI-2 solution having a solidamount of 8 wt % btained from Preparation Example 8 were introduced into70 g of a PAA-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 1, agitated while flowing nitrogen for 24 hours,then filtered though a filter having a sieve size of 0.1 μm to provide aphotoalignment agent of a liquid crystal (hereinafter referred to asPAA/SPI/PSPI-5) having a solid amount of 8 wt %.

Example 8

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 30 g of a PSPI-2 solution having a solidamount of 8 wt % obtained from Preparation Example 8 were introducedinto 50 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-6) having a solid amount of 8 wt %.

Example 9

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 50 g of a PSPI-2 solution having a solidamount of 8 wt % obtained from Preparation Example 8 were introducedinto 30 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a sieve size of 0.1 μm toprovide a photoalignment agent of a liquid crystal (hereinafter referredto as PAA/SPI/PSPI-7) having a solid amount of 8 wt %.

Example 10

20 g of an SPI-1 solution having a solid amount of 8 wt % obtained fromPreparation Example 4 and 70 g of a PSPI-12 solution having a solidamount of 8 wt % obtained from Preparation Example 8 were introducedinto 10 g of a PAA-1 solution having a solid amount of 8 wt % obtainedfrom Preparation Example 1, agitated while flowing nitrogen for 24hours, then filtered though a filter having a particle diameter of 0.1μm to provide a photoalignment agent of a liquid crystal (hereinafterreferred to as PAA/SPI/PSPI-8) having a solid amount of 8 wt %.

Comparative Example 1

The photoalignment solution (PSPI-1) having a solid amount of 8 wt %obtained from Preparation Example 7 was filtered with a 0.1 μm filter toprovide a photoalignment agent of a liquid crystal having a solid amountof 8 wt %.

Comparative Example 2

The photoalignment solution (PSPI-2) having a solid amount of 8 wt %obtained from Preparation Example 8 was filtered with a 0.1 μm filter toprovide a photoalignment agent of a liquid crystal having a solid amountof 8 wt %.

Comparative Example 3

The photoalignment solution (PSPI-3) having a solid amount of 8 wt %obtained from Preparation Example 9 was filtered with a 0.1 μm filter toprovide a photoalignment agent of a liquid crystal having a solid amountof 8 wt %.

Comparative Example 4

The photoalignment solution (PSPI-4) having a solid amount of 8 wt %obtained from Preparation Example 10 was filtered with a 0.1 μm filterto provide a photoalignment agent of a liquid crystal having a solidamount of 8 wt %.

Comparative Example 5

The photoalignment solution (PSPI-5) having a solid amount of 8 wt %obtained from Preparation Example 11 was filtered with a 0.1 μm filterto provide a photoalignment agent of a liquid crystal having a solidamount of 8 wt %.

(Printability of Liquid Crystal Photo-alignment Film)

Each of crystal liquid alignment agents obtained from Examples 1 to 8and Comparative Examples 1 and 2 was coated on an ITO substrate having asize of 10 cmx 10 cm under a certain condition in a uniform thickness of0.1 μm in accordance with a spin coating method, and solvent was removedon a hot plate at a temperature of 70° C. Then it was cured at atemperature of 210° C. to provide a liquid crystal photoalignment film.

The obtained liquid crystal alignment films were observed for thediffusion characteristic and the rolling characteristic via the nakedeye and an optical microscope to determine the printability of thephotoalignment agent of a liquid crystal. The results of theprintability determination are shown in the following Table 1.

(Liquid Crystal Alignment Properties of Liquid Crystal Photo-alignmentFilm)

A liquid crystal cell was fabricated to determine liquid crystalalignment properties of a photoalignment agent of a liquid crystal. Theliquid crystal cell was fabricated by the following processes

An ITO glass substrate having a standardized size was patterned viaphotolithography in order to produce 1.5 cm×1.5 cm ITO substrates withan ITO electrode for applying a voltage.

Each of photoalignment agents of a liquid crystal obtained from Examples1 to 8 and Comparative Examples 1 and 2 was coated on a patterned ITOsubstrate at a thickness of 0.1 μm by spin coating and cured at 70° C.and 210° C.

Two of the cured ITO substrates were exposed at a certain angle by acertain energy with an exposer (UIS-S2021J7-YD01, Ushio LPUV), placed inopposite directions to each other (for VA mode, 90 degree) to arrangethe square ITO shape of the top to correspond to that of the bottom, andjoined while maintaining a cell gap of 4.75 μm. The light source forexposure was a 2 kW deep UV ramp (UXM-2000).

The obtained cell was filled with liquid crystal, and the liquid crystalalignment properties were observed with a perpendicularly-polarizedoptical microscope. The results are shown in the following Table 1.

(Pretilt Angle of Liquid Crystal Photo-alignment Film)

In order to observe the pretilt angle, a separate liquid crystal cellwas fabricated to maintain a cell gap of 50 μm.

The liquid crystal cell having a cell gap of 50 μm was fabricated andmeasured by a crystal rotation method to determine the pretilt angle forthe liquid crystal alignment agents obtained Example 1 to 8, ComparativeExample 1, and Comparative Example 2. The results of measuring thepretilt angle are shown in the following Table 1.

(Electrical Characteristic and Optical Characteristic of Liquid Crystal

Photo-alignment Film)

The electrical characteristic and the optical characteristic of theliquid crystal photoalignment films having a cell gap of 4.75 μm weremeasured to determine a voltage-transmission curved line, a voltageholding ratio, and a residual DC voltage.

The voltage-transmission curved line, the voltage holding ratio, and theelectrical and optical characteristics of residual DC-voltage arebriefly described as follows.

The voltage-transmission curved line is one of the important electricaland optical characteristics, and one determining the driving voltage fora liquid crystal display (LCD). This is a standardized curve byconsidering the quantity of light of the brightest state as 100%, andthe quantity of light of the darkest state as 0% when a voltage isapplied to the liquid crystal cell for measuring the transmission.

The voltage holding ratio is determined as a degree at which thefloating liquid crystal layer (with the external electric source)maintains the charged voltage for an unselected period in an activematrix TFT-LCD. The value is more ideal as it approaches 100%.

The residual DC voltage indicates a voltage that is applied to theliquid crystal layer when the external voltage is not applied, due tothe ionized impurities of the liquid crystal layer that are absorbed onthe alignment film. The value is more ideal as it becomes lower. Thecommon method of measuring the residual DC voltage includes a methodusing flicker and a method using an electrical capacity changing curvedline (C−V) of the liquid crystal layer depending upon the DC voltage.

The results of the electrical and optical characteristics of the liquidcrystal photoalignment film using the liquid crystal cell are shown inthe following Table 2.

TABLE 1 Vertical Photo- Pretilt alignment alignment angle MaterialPrintability properties properties (°) Example 1 good good good 89.86Example 2 good good good 89.91 Example 3 good good good 89.94 Example 4good good good 89.88 Example 5 good good good 89.91 Example 6 good goodgood 89.95 Example 7 good good good 89.88 Example 8 good good good 89.90Comparative good good good 89.89 Example 1 Comparative good good good89.90 Example 2

TABLE 2 Voltage holding ratio (%) Room High Voltage- temperaturetemperature Residual DC Material transmission 25° C. 60° C. (by C-V)Example 1 good 99.53 99.36 48 Example 2 good 99.55 99.32 46 Example 3good 99.51 99.28 51 Example 4 good 99.52 99.26 45 Example 5 good 99.4899.18 60 Example 6 good 99.51 99.16 58 Example 7 good 99.56 99.15 61Example 8 good 99.47 99.12 55 Comparative good 98.51 97.31 332 Example 1Comparative good 98.38 97.08 401 Example 2

Referring to Table 1, it is indicated that the photoalignment agents ofa liquid crystal according to Examples 1 to 8 had sufficientprintability, vertical alignment properties, photoalignment properties,and pretilt angle to be used in a liquid crystal photoalignment film.

Referring to Table 2, the photoalignment agents of a liquid crystalaccording to Examples 1 to 8 had good voltage-transmission, and avoltage holding ratio of 99% or more. On the other hand, the voltageholding ratio of the photoalignment agents of a liquid crystal accordingto Comparative Examples 1 and 2 did not reach 99%.

Furthermore, the photoalignment agents of a liquid crystal obtained fromExamples 1 to 8 had low residual DC, while the photoalignment agents ofa liquid crystal obtained from Comparative Examples 1 and 2 hadrelatively high residual DC.

The voltage holding ratio and the residual DC are references fordetermining the after-image characteristics of the liquid crystalphotoalignment film. The after-image characteristics can be improved asthe voltage holding ratio becomes higher and the residual DC becomeslower. Accordingly, the photoalignment agents of a liquid crystalobtained from Examples 1 to 8 had better after-image characteristicsthan those of the liquid crystal photoalignment agents obtained fromComparative Examples 1 and 2.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A liquid crystal photoalignment agent comprising: a compound selectedfrom the group consisting of polyamic acid represented by the followingChemical Formula 1, polyimide polymers represented by the followingChemical Formula 2, and combinations thereof; and a polyimidephotopolymer represented by the following Chemical Formula 3,

wherein, in the above Formulae 1 to 3, R₁, R₃, and R₅ are independentlya quadrivalent organic group derived from an acid dianhydride selectedfrom the group consisting of aliphatic cyclic acid dianhydrides andaromatic acid dianhydrides, R₂ and R₄ are independently a divalentorganic group derived from an aromatic diamine, and R₆ is a divalentorganic group derived from a photodiamine selected from the groupconsisting of cumarin-based photodiamines, chalcone-based photodiamines,and cinnamate-based photodiamines.
 2. The liquid crystal photoalignmentagent of claim 1, wherein the aliphatic cyclic acid dianhydride isselected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylicacid dianhydride (CBDA),5-(2,5-dioxotetrahydrofuryl)-3-methylcyclohexene-1,2-dicarboxylic acidanhydride (DOCDA), bicyclooctene-2,3,5,6-tetracarboxylic aciddianhydride (BODA), 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride(CPDA), 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (CHDA),1,2,4-tricarboxyl-3-methylcarboxyl cyclopentane dianhydride,1,2,3,4-tetracarboxyl cyclopentane dianhydride, and combinationsthereof.
 3. The liquid crystal photoalignment agent of claim 1, whereinR₁, R₃, and R₅ are independently selected from the group consisting ofcompounds represented by the following Chemical Formulae 4 to 8, andcombinations thereof:

wherein, in the above Formulae 4 to 8, R₁₀ is selected from the groupconsisting of a substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl, and n₁₀ is an integer ranging from 0to 3, and R₁₁ to R₁₇ are independently selected from the groupconsisting of hydrogen, a substituted or unsubstituted C1 to C20 alkyl,substituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl.
 4. The liquid crystal photoalignmentagent of claim 1, wherein the aromatic acid dianhydride is selected fromthe group consisting of pyromellitic acid dianhydride (PMDA), biphthalicacid dianhydride (BPDA), oxydiphthalic acid dianhydride (ODPA),benzophenone tetracarboxylic acid dianhydride (BTDA),hexafluoroisopropylidene diphthalic acid dianhydride (6-FDA), andcombinations thereof.
 5. The liquid crystal photoalignment agent ofclaim 1, wherein R₁, R₃, and R₅ are independently selected from thegroup consisting of compounds represented by the following Formula 9,compounds represented by the following Formula 10, and a combinationsthereof:

wherein, in the above Formulae 9 and 10, R₂₁ and R₂₂ are independentlyselected from the group consisting of hydrogen, a substituted orunsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 to C30aryl, and a substituted or unsubstituted C2 to C30 heteroaryl, R₂₄ andR₂₅ are independently selected from the group consisting of asubstituted or unsubstituted C1 to C20 alkyl, a substituted orunsubstituted C1 to C30 aryl, and substituted or unsubstituted C2 to C30heteroaryl, and n₂₄ and n₂₅ are independently integers ranging from 0 to3, and R₂₃ is selected from the group consisting of O, CO, substitutedor unsubstituted C1 to C6 alkylene, substituted or unsubstituted C3 toC30 cycloalkylene, and substituted or unsubstituted C2 to C30heterocycloalkylene, and n₂₃ is an integer of 0 or
 1. 6. The liquidcrystal photoalignment agent of claim 1, wherein the aromatic diamine isselected from the group consisting of paraphenylenediamine (p-PDA),4,4-methylene dianiline (MDA), 4,4-oxydianiline (ODA),metabisaminophenoxydiphenylsulfone (m-BAPS),parabisaminophenoxydiphenylsulfone (p-BAPS),2,2-bis[(aminophenoxy)phenyl]propane (BAPP),2,2-bisaminophenoxyphenylhexafluoropropane (HF-BAPP),1,4-diamino-2-methoxybenzene, and combinations thereof.
 7. The liquidcrystal photoalignment agent of claim 1, wherein R₂ and R₄ areindependently selected from the group consisting of compoundsrepresented by the following Chemical Formulae 11 to 13, andcombinations thereof:

wherein, in the above Formulae 11 to 13, R₃₁, R₃₃, R₃₄, and R₃₇ to R₄₀are independently selected from the group consisting of substituted orunsubstituted C1 to C20 alkyl, a substituted or unsubstituted C1 to C30aryl, substituted or unsubstituted C2 to C30 heteroaryl, and alkyl,aryl, and heteroaryl substituted with —O—, —COO—, —CONH—, —OCO—, or acombinations thereof, R₃₀, R₃₂, R₃₅, and R₃₆ are independently selectedfrom the group consisting of O, SO₂, and C(R′)(R″), wherein R′ and R″are independently selected from the group consisting of hydrogen and asubstituted or unsubstituted C1 to C6 alkyl, n₃₁, n₃₃, n₃₄, and n₃₇ ton₄₀ are independently integers ranging from 0 to 4, and n₃₀, n₃₂, n₃₅,and n₃₆ are independently integers of 0 or
 1. 8. The liquid crystalphotoalignment agent of claim 1, wherein the aromatic diamine is afunctional diamine selected from the group consisting of compounds ofthe following Chemical Formulae 14 to 16:

wherein, in the above Formula 14, R₄₁ is selected from the groupconsisting of hydrogen, substituted or unsubstituted C1 to C20 alkyl,substituted or unsubstituted C1 to C30 aryl, and a substituted orunsubstituted C2 to C30 heteroaryl, and R₄₂ is selected from the groupconsisting of a substituted or unsubstituted C1 to C20 alkyl,substituted or unsubstituted C1 to C30 aryl, and substituted orunsubstituted C2 to C30 heteroaryl, and n₄₂ is an integer ranging from 0to 3,

wherein, in the above Formula 15, R₄₃, R₄₅, and R₄₆ are independentlyselected from the group consisting of substituted or unsubstituted C1 toC20 alkyl, a substituted or unsubstituted C1 to C30 aryl, and asubstituted or unsubstituted C2 to C30 heteroaryl, R₄₄ is selected fromthe group consisting of O, COO, CONH, OCO, and a substituted orunsubstituted C1 to C10 alkylene, R₄₇ is selected from the groupconsisting of hydrogen, substituted or unsubstituted C1 to C20 alkyl, asubstituted or unsubstituted C1 to C30 aryl, substituted orunsubstituted C2 to C30 heteroaryl, and alkyl, aryl, and a heteroarylsubstituted with —O—, —COO—, —CONH—, —OCO—, or a combinations thereof,n₄₃ is an integer of 0 or 3, n₄₅ and n₄₆ are independently integersranging from 0 to 4, and n₄₄ is an integer of 0 or 1,

wherein, in the above Formula 16, R₆₄ and R₆₆ are independently selectedfrom the group consisting of substituted or unsubstituted C1 to C20alkyl, substituted or unsubstituted C1 to C30 aryl, and substituted orunsubstituted C2 to C30 heteroaryl, R₆₅ is a selected from the groupconsisting of hydrogen, substituted or unsubstituted C1 to C20 alkyl,substituted or unsubstituted C1 to C30 aryl, and substituted orunsubstituted C2 to C30 heteroaryl, R₆₁ and R₆₂ are independentlyselected from the group consisting of O and COO, R₆₃ is selected fromthe group consisting of O, COO, CONH, and OCO, n₆₄ and n₆₆ areindependently integers ranging from 0 to 4, and n₆₁ to n₆₃ areindependently integers of 0 or
 1. 9. The liquid crystal photoalignmentagent of claim 1, wherein the cinnamate-based photodiamine is selectedfrom the group consisting of compounds of the following Formula 17,compounds of the following Formula 18, and combinations thereof:

wherein, in the above Formula 17, R₇₁ is selected from the groupconsisting of hydrogen, substituted or unsubstituted C1 to C30 alkyl,substituted or unsubstituted C6 to C30 aryl, and substituted orunsubstituted C2 to C30 heteroaryl, and R₇₂ is selected from the groupconsisting of substituted or unsubstituted C1 to C30 alkyl, substitutedor unsubstituted C6 to C30 aryl, and substituted or unsubstituted C2 toC30 heteroaryl, and n₇₂ is an integer ranging from 0 to 3,

wherein, in the above Formula 18, R₇₇ is selected from the groupconsisting of aromatic diamines, diamines including a substituted orunsubstituted linear or branched C1 to C24 alkylene, and combinationsthereof, wherein the substituted alkylene of R₇₇ is selected from thegroup consisting of substituted alkylene wherein hydrogen is substitutedwith a substituent selected from the group consisting of halogen andcyano, substituted alkylene wherein at least one CH₂ group issubstituted with a substituent selected from the group consisting of asubstituted or unsubstituted C2 to C30 arylene, substituted orunsubstituted C2 to C30 heteroarylene, a substituted or unsubstituted C3to C30 cycloalkylene, substituted or unsubstituted C2 to C30heterocycloalkylene, —O—, —CO—, —CO—O—, —O—CO—, —Si(CH₃)₂—O—Si(CH₃)₂—,—NR′—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—, —O—CO—NR′—, —NR′—, —CO—NR′—,—CH═CH—, —C≡C—, and —O—CO—O—, wherein (R′ is selected from the groupconsisting of hydrogen and substituted or unsubstituted C1 to C6 alkyl,and wherein adjacent CH₂ groups are not substituted, and combinationsthereof, R₇₄ is selected from the group consisting of substituted orunsubstituted C1 to C20 alkyl, substituted or unsubstituted C1 to C30aryl, and substituted or unsubstituted C2 to C30 heteroaryl, and n₇₄ isan integer ranging from 0 to 4, R₇₅ and R₇₆ are independently selectedfrom the group consisting of hydrogen, halogen, cyano, and substitutedor unsubstituted C1 to C12 alkyl, wherein the substituted alkyls of R₇₅and R₇₆ are selected from the group consisting of substituted alkylwherein hydrogen is substituted with a substituent selected from thegroup consisting of halogen and cyano, substituted alkyl wherein atleast one CH₂ group is substituted with a substituent selected from thegroup consisting of —O—, —OC—O—, —O—CO—, and —CH═CH—, wherein adjacentCH₂ groups are not substituted, and combinations thereof, R₇₃ isselected from the group consisting of substituted or unsubstituted C1 toC30 alkyl, substituted or unsubstituted C7 to C30 alkylaryl, substitutedor unsubstituted C3 to C30 cycloalkyl, substituted or unsubstitutedpyrimidinyl, substituted or unsubstituted pyridinyl, substituted orunsubstituted thiophenyl, substituted or unsubstituted furanyl,substituted or unsubstituted naphthyl, and a substituted orunsubstituted phenyl, wherein the substituted alkyl of R₇₃ is selectedfrom the group consisting of substituted alkyl wherein hydrogen issubstituted with a substituent selected from the group consisting ofhalogen and cyano, substituted alkyl wherein at least one CH₂ group issubstituted with a substituent selected from the group consisting of—O—, —CO—O—, —O—CO—, and —CH═CH—, wherein adjacent CH₂ groups are notsubstituted, and combinations thereof, and wherein the substitutedalkylaryl of R₇₃ is a substituted alkylaryl where at least one CH₂ groupis substituted with a substituent selected from the group consisting of—O—, —OC—O—, —O—CO—, —CH═CH—, and combinations thereof, wherein adjacentCH₂ groups are not substituted.
 10. The liquid crystal photoalignmentagent of claim 1, wherein the chalcone-based photodiamine is a compoundof the following Formula 19:

wherein, in the above Formula 19, R₈₁ is selected from the groupconsisting of aromatic diamines, diamines including a substituted orunsubstituted linear or branched C1 to C24 alkylene, and combinationsthereof, wherein the substituted alkylene of R₈₁ is selected from thegroup consisting of substituted alkylene wherein hydrogen is substitutedwith a substituent selected from the group consisting of halogen andcyano, a substituted alkylene where at least one CH₂ group issubstituted with a substituent selected from the group consisting ofsubstituted or unsubstituted C2 to C30 arylene, substituted orunsubstituted C2 to C30 heteroarylene, a substituted or unsubstituted C3to C30 cycloalkylene, substituted or unsubstituted C2 to C30heterocycloalkylene, —O—, —CO—, —CO—O—, —O—CO—, —Si(CH₃)₂—O—Si(CH₃)₂—,—NR′—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—, —O—CO—NR′—, —NR′—, —CO—NR′—,—CH═CH—, —C≡C— and —O—OC—O—, wherein (R′ is selected from the groupconsisting of hydrogen and substituted or unsubstituted C1 to C6 alkyl,and wherein adjacent CH₂ groups are not substituted, and combinationsthereof, R₈₂ and R₈₅ are selected from the group consisting ofsubstituted or unsubstituted C1 to C20 alkyl, substituted orunsubstituted C1 to C30 aryl, and substituted or unsubstituted C2 to C30heteroaryl, and n₈₂ and n₈₅ are integers ranging from 0 to 4, R₈₃ andR₈₄ are independently selected from the group consisting of hydrogen,halogen, cyano, and substituted or unsubstituted C1 to C12 alkyl,wherein the substituted alkyls of R₈₃ and R₈₄ are selected from thegroup consisting of substituted alkyl wherein hydrogen is substitutedwith a substituent selected from the group consisting of halogen andcyano, substituted alkyl wherein at least one CH₂ group is substitutedwith a substituent selected from the group consisting of —O—, —CO—O—,—O—CO—, and —CH═CH—, wherein adjacent CH₂ groups are not substituted,and combinations thereof, R₈₆ is selected from the group consisting ofsubstituted or unsubstituted C1 to C30 alkyl, substituted orunsubstituted C7 to C30 alkylaryl, substituted or unsubstituted C3 toC30 cycloalkyl, substituted or unsubstituted pyrimidinyl, substituted orunsubstituted pyridinyl, substituted or unsubstituted thiophenyl,substituted or unsubstituted furanyl, substituted or unsubstitutednaphthyl, and substituted or unsubstituted phenyl, wherein thesubstituted alkyl of R₈₆ is selected from the group consisting ofsubstituted alkyl wherein hydrogen is substituted with substituentselected from the group consisting of halogen and a cyano, substitutedalkyl where at least one CH₂ group is substituted with a substituentselected from the group consisting of —O—, —CO—O—, —O—CO—, and —CH═CH—,wherein adjacent CH₂ groups are not substituted, and combinationsthereof, and wherein the substituted alkylaryl of R₈₆ is a substitutedalkylaryl wherein at least one CH₂ group is substituted with asubstituent selected from the group consisting of —O—, —OC—O—, —O—CO—,—CH═CH—, and combinations thereof, wherein adjacent CH₂ groups are notsubstituted.
 11. The liquid crystal photoalignment agent of claim 1,wherein the cumarin-based photodiamine is a compound of the followingFormula 20:

wherein, in the above Formula 20, R₉₁ is selected from the groupconsisting of aromatic diamines, diamines including substituted orunsubstituted linear or branched C1 to C24 alkylene, and combinationsthereof, wherein the substituted alkylene of R₉₁ is selected from thegroup consisting of substituted alkylene wherein hydrogen is substitutedwith a substituent selected from the group consisting of halogen andcyano, substituted alkylene wherein at least one CH₂ group issubstituted with a substituent selected from the group consisting ofsubstituted or unsubstituted C2 to C30 arylene, substituted orunsubstituted C2 to C30 heteroarylene, substituted or unsubstituted C3to C30 cycloalkylene, a substituted or unsubstituted C2 to C30heterocycloalkylene, —O—, —CO—, —CO—O—, —O—CO—, —Si(CH₃)₂—O—Si(CH₃)₂—,—NR′—, —NR′—CO—, —CO—NR′—, —NR′—CO—O—, —O—CO—NR′—, —NR′—, —CO—NR′—,—CH═CH—, —C≡C—, and —O—OC—O—, wherein (R′ is selected from the groupconsisting of hydrogen and a substituted or unsubstituted C1 to C6alkyl, and wherein adjacent CH₂ groups are not substituted, andcombinations thereof, R₉₂ is selected from the group consisting ofsubstituted or unsubstituted C1 to C20 alkyl, substituted orunsubstituted C1 to C30 aryl, and substituted or unsubstituted C2 to C30heteroaryl, and n₉₂ is an integer ranging from 0 to 4, R₉₃ and R₉₄ areindependently selected from the group consisting of hydrogen, halogen,cyano, and substituted or unsubstituted C1 to C12 alkyl, and wherein thesubstituted alkyls of R₉₃ and R₉₄ are selected from the group consistingof substituted alkyl wherein hydrogen is substituted with a substituentselected from the group consisting of halogen and cyano, substitutedalkyl wherein at least one CH₂ group is substituted with a substituentselected from the group consisting of —O—, —OC—O—, —O—CO—, and —CH═CH—,wherein adjacent CH₂ groups are not substituted, and combinationsthereof.
 12. The liquid crystal photoalignment agent of claim 1, whereinthe liquid crystal photoalignment agent comprises 1 to 90 parts byweight of the polyamic acid or 1 to 50 parts by weight of the polyimidepolymer, and 0.001 to 90 parts by weight of the polyimide photopolymer.13. The liquid crystal photoalignment agent of claim 12, wherein theliquid crystal photoalignment agent comprises 1 to 90 parts by weight ofthe polyamic acid or 1 to 40 parts by weight of the polyimide polymer,and 1 to 60 parts by weight of the polyimide photopolymer.
 14. Theliquid crystal photoalignment agent of claim 1, wherein the liquidcrystal photoalignment agent comprises 1 to 90 parts by weight of thepolyamic acid, 1 to 50 parts by weight of the polyimide polymer, and 1to 90 parts by weight of the polyimide photopolymer.
 15. A liquidcrystal photoalignment film fabricated by applying the liquid crystalphotoalignment agent according to claim 1 on a substrate.
 16. A liquidcrystal display (LCD) comprising the liquid crystal photoalignment filmaccording to claim 15.